Dispensing devices such as caulking guns are well known for dispensing viscous material. The dispensing devices can either be fully enclosed, where the viscous material is loaded into a sealed container; or the dispensing device can have an opening designed to receive a "drop-in" cartridge. The drop-in type dispensing devices typically include a pistol-grip handle with connection at the forward end to a conventional frame structure including a butt cup, a hemispherical cylinder extending forwardly from the butt cup, and a yoke at the distal end of the cylinder. A plunger shank or shaft passes horizontally through the upper portion of the handle and has at its rear end a substantially right-angle bend, and at its forward end a piston plate for urging the viscous material from a conventional cylindrical cartridge held between the butt cup and the yoke in the hemispherical cylinder. Such a drop-in type dispensing device is shown in Chang, U.S. Pat. No. 4,081,112.
Various techniques have been developed to drive the plunger shaft forwardly within the hemispherical cylinder to dispense the viscous material. The most commonly known technique is to have a trigger driving a spring-biased washer off-center against the plunger shaft to grab and advance the shaft. The trigger engages the bottom portion of the washer during each manual stroke of the trigger. An improvement of this technique is shown in Chang, U.S. Pat. No. 4,081,112, whereby the trigger engages the upper portion of the washer during each manual stroke. Another improved technique is shown in Davis, Jr., U.S. Pat. No. 4,376,498, which uses compressed air to drive the plunger shaft forward. An even more recent technique is shown in Anderson, et al., U.S. Pat. No. 5,181,636, which is owned by the assignee of the present invention, wherein compressed air or CO.sub.2 is used to drive a washer off-center to grab and advance the plunger shaft.
After the plunger shaft has been driven forwardly to dispense a sufficient amount of viscous material, or when the cartridge is depleted, a release trigger can be manipulated to allow the plunger shaft to be moved in a reverse direction.
The above discussion tends to show that, while a certain amount of development has been directed toward the means for driving the plunger shaft forward to dispense the viscous material, little innovation has occurred in the hemispherical cylinder supporting the cylindrical cartridge.
It has been applicants' experience that particularly with the development of compressed air-driven and CO.sub.2 -driven caulking guns, the plunger piston in the dispensing device is being driven forward within the cartridge with considerable force. It is also applicants' experience that under some situations, the cartridge can become misaligned or askew within the hemispherical cylinder. For example, the cartridge can become misaligned if the piston within the cartridge tilts while dispensing a low viscosity material and the plunger piston raises the rear end of the cartridge from its seat within the cylinder; or when pressure is applied to the nozzle of the cartridge during dispensing of the material (e.g., the nozzle is forced into a wall joint to apply caulk--which thereby moves the cartridge rearwardly within the caulking gun and offsets the front end of the cartridge from the yoke).
If the cartridge is somehow askew or misaligned within the dispensing device, the caulking cartridge can exert a concentrated load against the front yoke or on support structure on the device and damage the dispensing device when the trigger piston advances. Applicants' have determined that this may be due to the front end of the cartridge becoming misaligned with or dislodged from the front yoke of the device such that when the plunger piston advances against the cartridge piston, the front cap on the cartridge is driven at an angle against the yoke, or into the surrounding structure on the device--for example the peripheral flange on the front yoke.
Hence, applicants have determined that there is a demand in the industry for a dispensing device which prevents misalignment of a cartridge when the viscous product is being dispensed.